Cameras were not allowed in the courtroom Wednesday, but video from a previous hearing shows the defendants -- Jesus Reynoso Flores and Jose Ventura.
Authorities say they murdered 18-year-old Alberto Ivan Torres just 20 minutes into his first day on the job at a dairy near Chowchilla in 2008.
Surveillance video captured the execution-style shooting, which a second victim survived.
Torres' uncle told Action News he doesn't want to attend the trial because it's too hard for him to see the men accused of killing his nephew.
"Everyone who knew Ivan, he was such good guy," said Eduardo Torres. "He didn't do nothing wrong to nobody. Everybody who was close to him they really love him."
Much of the testimony Wednesday afternoon centered around audio recordings, which witnesses say captured Jesus Flores talking about the murder.